Saikia Karabi, Chaudhary Nitin
Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781 039, India.
Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781 039, India.
Biochem Biophys Res Commun. 2018 Mar 25;498(1):58-63. doi: 10.1016/j.bbrc.2018.02.176. Epub 2018 Feb 23.
Antimicrobial peptides are critical components of defense systems in living forms. The activity is conferred largely by the selective membrane-permeabilizing ability. In our earlier work, we derived potent antimicrobial peptides from the 9-residue long, N-terminal amphipathic helix of E. coli MreB protein. The peptides display broad-spectrum activity, killing not only Gram-positive and Gram-negative bacteria but opportunistic fungus, Candida albicans as well. These results proved that membrane-binding stretches of bacterial proteins could turn out to be self-harming when applied from outside. Here, we studied the membrane-binding and membrane-perturbing potential of these peptides. Steady-state tryptophan fluorescence studies with tryptophan extended peptides, WMreB and its N-terminal acetylated analog, Ac-WMreB show preferential binding to negatively-charged liposomes. Both the peptides cause permeabilization of E. coli inner and outer-membranes. Tryptophan-lacking peptides, though permeabilize the outer-membrane efficiently, little permeabilization of the inner-membrane is observed. These data attest membrane-destabilization as the mechanism of rapid bacterial killing. This study is expected to motivate the research in identifying microbes' self-sequences to combat them.
抗菌肽是生物防御系统的关键组成部分。其活性主要由选择性膜通透能力赋予。在我们早期的工作中，我们从大肠杆菌MreB蛋白9个残基长的N端两亲性螺旋中获得了强效抗菌肽。这些肽具有广谱活性，不仅能杀死革兰氏阳性菌和革兰氏阴性菌，还能杀死机会性真菌白色念珠菌。这些结果证明，细菌蛋白的膜结合片段从外部应用时可能会自我伤害。在此，我们研究了这些肽的膜结合和膜扰动潜力。用色氨酸延伸肽WMreB及其N端乙酰化类似物Ac-WMreB进行的稳态色氨酸荧光研究表明，它们优先结合带负电荷的脂质体。这两种肽都会导致大肠杆菌内膜和外膜的通透化。缺乏色氨酸的肽虽然能有效通透外膜，但内膜的通透化程度很小。这些数据证明膜去稳定化是快速杀菌的机制。这项研究有望推动识别微生物自身序列以对抗它们的研究。
